The U.S. Environmental Protection Agency (EPA) estimates that approximately 250 million scrap tires are generated in the United States each year. In the United States alone, the Rubber Manufacturers Association (RMA) has estimated that between two and three billion scrap tires currently reside in landfills or are otherwise stockpiled. Waste tires take up a significant amount of space in landfills, and burying of the tires can lead to landfill contamination. Stockpiling waste tires provides breeding grounds for pests and represents a significant fire hazard. Burning of tires causes a significant amount of air pollution, and run-off from tire fires can contaminate ground water. The handling and disposal of waste tires is a significant environmental problem, and the desirability of recycling waste is evident.
One method of recycling waste tires is pyrolysis. Known tire pyrolysis processes include heating tires to produce useful products such as oils, gases, recyclable metals, and carbonaceous char. As disclosed in U.S. Pat. Nos. 5,783,046, 6,372,948, and 7,037,410 to Flanigan, the entire disclosures of which are hereby incorporated herein by reference, a known pyrolysis process includes heating rubber in the substantial absence of oxygen to a temperature sufficient to pyrolyze the rubber, distilling a vapor comprising hydrocarbon from the rubber, and producing a solid carbonaceous char. Weinecke et al. in U.S. Pat. No. 7,101,463, hereby incorporated herein by reference in its entirety, describes a system and process for the recovery of oil from shredded vehicle tires that utilizes a pair of sequentially positioned packed towers. Also disclosed in U.S. Pat. No. 5,894,012 to Denison, hereby incorporated herein by reference in its entirety, is a waste processing system that produces clear and colorless oil for use in rubber and plastic applications and a carbonaceous char equivalent to a low structure furnace black.
Another known tire pyrolysis process is described in U.S. Pat. Nos. 6,835,861 and 7,341,646 to Nichols et al., the entire disclosures of which are hereby incorporated herein by reference. The method includes heating a hydrocarbon material while maintaining a vacuum, using a clay catalyst. The temperature of the reaction chamber and corresponding fuel input is varied either over time or spatially within the reaction chamber, to take advantage of the exothermic properties of the reaction.
There is a continuing need for a waste recycling process that produces a carbon black product suitable for use in rubber, plastic, and other commercial applications. Desirably, the process also produces fuel-grade oil, recyclable metal, gas, energy, and other marketable products.